Is there a way to select a new Ground handling / catering agent to specific airport other than changing settings per each parking position? For exemple at LROP, I want to use DNATA as per real life. I have read the info on it in a manual, but I still cant figure it out
Almost all editor settings in GSX can be applied to multiple parking spots, which can be individually selected with CTRL-click, or by selecting their "parent" node. For a single parking, their group ( Gate A, Gate B, Parking ,etc. ) is the parent so, if you click that one, it will select all parking spots of that group. And the same is valid for the root node, the "Airport", which if selected, will select ALL parking spots of the airport.
Once multiple parking spots are selected, if you make a change, it will affect all the selected ones so, in your case, if you assign an operator when the Airport is selected, it will be assigned to all parking spots of the airport.